This invention relates to a permanent magnet synchronous linear motor that has a reduced cogging thrust and that is superior in performance.
Conventionally, there is known a permanent magnet synchronous linear motor that is used for a feed mechanism of a machine tool or for a positioning device of a semiconductor manufacturing apparatus and that includes permanent magnets constituting a field pole and an armature facing the pole face of the permanent magnets through an air gap and in which an armature winding is wound in a slot of an armature core.
A cogging thrust is generated due to an edge effect at both ends of the armature core when the armature is moved in the longitudinal direction of the magnet array of the permanent magnets due to an electromagnetic effect with the permanent magnets in a state where an electric current is not passed through the armature winding of such a structured linearmotor. In order to reduce this cogging thrust, a linear motor that has auxiliary teeth at both ends of the armature core has been proposed as a conventional technique described as follows.
FIG. 5 is a side sectional view of a permanent magnet synchronous linear motor that shows a first conventional technique that uses the 8-pole and 9-slot gap-opposed type (see JP,7-053427,Y2 for example).
In FIG. 5, 1 is a flat field yoke, 2 is a plurality of permanent magnets disposed on the field yoke 1 so as to alternate the polarity thereof, 10 is an armature facing the pole face of the permanent magnet 2 through an air gap, and 11 is an armature core in which an electromagnetic steel plate is pectinately cut and in which an armature-core disc that has main teeth 11b forming slots 11a and a yoke portion 11c by which main teeth 11b are connected is placed and fixed thereto. 12 is an armature winding wound and contained in the slot 11a. 13 are auxiliary teeth provided at both ends of the armature core 11, and the length Ht of the main teeth 11b is equal to the length Hd of the auxiliary teeth 13. In this linear motor, the permanent magnets 2 provided on the field yoke 1 serve as a stator, and the armature 10 serves as a movable part and runs in the longitudinal direction of the field yoke 1.
In such a structured linear motor, the distance between the centers of the auxiliary teeth is an odd number of times as large as half of a field-pole pitch, i.e., satisfies the relationship of xcfx84po=(2nxe2x88x921)xc3x97xcfx84m/2 where xcfx84po is the distance between the centers of the auxiliary teeth disposed at both ends of the armature, and xcfx84m is the field-pole pitch. FIG. 5 shows an example in which n=9.
Further, a linear motor disclosed in JP,60-30195,B can be mentioned as a second conventional technique.
In this linear motor, the distance xcfx84po between the centers of auxiliary teeth provided at both ends of an armature is an odd number of times as large as the field-pole pitch xcfx84m, and satisfies the relationship of xcfx84po=(2nxe2x88x921)xc3x97xcfx84m.
However, in the conventional techniques, the distance between the centers of the auxiliary teeth is specified as mentioned above as a countermeasure for which an edge effect at the ends of the armature core is removed, but the intention to improve performance in accordance with the usage of the linear motor conversely narrows design freedom, and therefore a cogging thrust cannot be reduced, and, disadvantageously, difficulties in improving the performance of the linear motor cannot be eliminated.
Additionally, the distance between the centers of the auxiliary teeth, which is specified by the conventional techniques, is calculated in consideration of a primary component in which a change occurs in the ratio of 1 cycle to 1 magnetic-pole pitch. Therefore, a great reducing effect is brought about on the primary component, but, if a secondary component or a high-order component is contained in a cogging waveform, a reducing effect on the high-order component is small, and a situation occurs in which cogging cannot be reduced.
Still additionally, there is a situation in which the pitch between the auxiliary teeth where a cogging reducing effect is maximized deviates from the aforementioned pitch specified by the conventional techniques because of, for example, an influence of a slot shape between the teeth of the armature.
The present invention has been made to solve the problems, and it is an object of the present invention to provide a high-performance permanent magnet synchronous linear motor that has a reduced cogging thrust.
In order to solve the problems, a first aspect of is characterized in that a permanent magnet synchronous linear motor comprises a field yoke having a plurality of permanent magnets which constitute field poles so that the polarity thereof is alternated and which are arranged linearly and an armature facing an array of the permanent magnets through a magnetic air gap, in which the armature comprises an armature core having main teeth and slots, an armature winding wound in the slots of the armature core, and auxiliary teeth provided at both ends of the armature core and in which the center-to-center distance xcfx84 of the auxiliary teeth and the pitch xcfx84m of the field poles satisfy a relationship xcfx84p=(2nxe2x88x921)xc3x97xcfx84m/2 (n is a positive integer) and in which the field pole and the armature are relatively moved under the condition that one of the field pole and the armature is caused to serve as a stationary element and the other one is caused to serve as a movable element, wherein the length of the auxiliary teeth results in a relationship of 0 less than Hd less than Ht where Hd is the length of the auxiliary teeth in the direction orthogonal to the array of the permanent magnets and Ht is the length of the main teeth in the direction orthogonal to the array of the permanent magnets.
Another aspect of the invention is characterized in that, in the permanent magnet synchronous linear motor according to the first aspect, the width Bd of the auxiliary teeth along the longitudinal direction of the array of the permanent magnets is set to be narrower than the width Bt of the main teeth along the longitudinal direction of the array of the permanent magnets.
Another aspect of the invention is characterized in that, in the permanent magnet synchronous linear motor according to the above aspects, the ratio Hd/Ht of the length Hd of the auxiliary teeth to the length Ht of the main teeth is set to be 0.5 less than Hd/Ht less than 1.
Yet another aspect of the invention is characterized in that, in the permanent magnet synchronous linear motor according to any one of the above aspects, the armature core is made up of a plurality of divided cores, and is formed such that a convex engagement part is provided on a side face of a yoke portion that constitutes the divided cores, and a concave engagement part is provided on an opposite side face thereof, and thereafter adjoining parts of the engagement parts are fitted and coupled with each other.
Yet another aspect of the invention is characterized in that a permanent magnet synchronous linear motor comprises a field yoke having a plurality of permanent magnets which constitute field poles so that the polarity thereof is alternated and which are arranged linearly and an armature facing the array of the permanent magnets through a magnetic air gap, in which the armature comprises an armature core having main teeth and slots, an armature winding wound in the slots of the armature core, and auxiliary teeth provided at both ends of the armature core and in which the center-to-center distance xcfx84p of the auxiliary teeth and the pitch 1m of the field poles satisfy a relationship xcfx84pxe2x89xa0(2nxe2x88x921)xc3x97xcfx84m/2 (n is a positive integer) and in which the field pole and the armature are relatively moved under the condition that one of the field pole and the armature is caused to serve as a stationary element and the other one is caused to serve as a movable element, wherein the length of the auxiliary teeth results in a relationship of 0 less than Hdxe2x89xa6Ht where Hd is the length of the auxiliary teeth in the direction orthogonal to the array of the permanent magnets and Ht is the length of the main teeth in the direction orthogonal to the array of the permanent magnets.
Another aspect of the invention is characterized in that, in the permanent magnet synchronous linear motor according to the fifth aspect, the ratio Hd/Ht of the length Hd of the auxiliary teeth to the length Ht of the main teeth is set to be 0.5xe2x89xa6Hd/Htxe2x89xa61.
Yet another aspect of the invention is characterized in that, in the permanent magnet synchronous linear motor according to one of the prior two aspects, the armature core is made up of a plurality of divided cores, and is formed such that a convex engagement part is provided on a side face of a yoke portion that constitutes the divided cores, and a concave engagement part is provided on an opposite side face thereof, and thereafter adjoining parts of the engagement parts are fitted and coupled with each other.
An eighth aspect of the invention is characterized in that a permanent magnet synchronous linear motor comprises a field yoke having a plurality of permanent magnets which constitute field poles so that the polarity thereof is alternated and which are arranged linearly and an armature facing the array of the permanent magnets through a magnetic air gap, in which the armature comprises an armature core having main teeth and slots, an armature winding wound in the slots of the armature core, and auxiliary teeth provided at both ends of the armature core, and in which the field pole and the armature are relatively moved under the condition that one of the field pole and the armature is caused to serve as a stationary element and the other one is caused to serve as a movable element, wherein the center-to-center distance xcfx84p of the auxiliary teeth and the pitch xcfx84m of the field poles satisfy a relationship (2nxe2x88x921) xcfx84m/8xcfx84pxe2x89xa6(2nxe2x88x921) xcfx84m/2 (n is a positive integer), and wherein the length of the auxiliary teeth results in a relationship of 0 less than Hdxe2x89xa6Ht where Hd is the length of the auxiliary teeth in the direction orthogonal to the array of the permanent magnets and Ht is the length of the main teeth in the direction orthogonal to the array of the permanent magnets.
Another aspect of the invention is characterized in that, in the permanent magnet synchronous linear motor according to the eighth aspect, the width Bd of the auxiliary teeth along the longitudinal direction of the array of the permanent magnets is set to be narrower than the width Bt of the main teeth along the longitudinal direction of the array of the permanent magnets.
Yet another aspect of the invention is characterized in that, in the permanent magnet synchronous linear motor according to the prior aspect, the armature core is made up of a plurality of divided cores, and is formed such that a convex engagement part is provided on a side face of a yoke portion that constitutes the divided cores, and a concave engagement part is provided on an opposite side face thereof, and thereafter adjoining parts of the engagement parts are fitted and coupled with each other.